Led array head

ABSTRACT

Disclosed is here an LED array head in which a light emitting section thereof is selectively caused to emit light wherein a fiber bundle constituted with a plurality of optical fibers is arranged with an end portion thereof to be located at a position in the vicinity of the light emitting section. The base member for retaining fiber bundle is a protection member to protect the LED array.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an LED array head to be used for anapparatus such as an LED printer using an electro-photography process.

2. Description of the Prior Art

The prior art LED array head will be described with reference to FIG. 6.

In FIG. 6, the device includes a ceramic substrate 1 on which an LEDchip 2 is disposed by the die bonding and a wire bonds 3 are disposed inthe LED chip 2 for each light emitting section 2a so as to supplyelectric power thereto. In order to protect the LED chip against aninterference from the external environment, a cover glass 33 is fixedonto the ceramic substrate 1. Above the light emitting section 2a of theLED chip 2, there is arranged a rod lens array 4 of the self-convergencetype retained by a mechanism not shown, thereby collecting the lightradiated from the light emitting section 2a onto such an object 5 to beexposed to the light as a photosensitive drum.

However, in the LED array head of the prior art, since the rod lensarray of the self-convergence type 4 is utilized, the distance betweenthe light emitting section 2a and the object 5 to be exposed to thelight is determined by the focal length of the rod lens array of theself-convergence type 4 and is hence quite long.

In addition, only a portion of the light radiated from the lightemitting section 2a reaches the rod lens array of the self-convergencetype 4 and the efficiency of light transmission to the object 5 is notsatisfactory; as a consequence, in order to increase the quantity oflight, a great energy is required to radiate light to be supplied to theLED chip 2.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide asmall-sized LED array which does not require such a large energy toradiate light, thereby removing the problem described above.

The representative feature of the present invention resides in that afiber bundle including a plurality of optical fibers is arranged with anend portion thereof located at a position in the neighborhood of a lightemitting section and that a base member retaining the fiber bundle is aprotection member of the LED array.

Since the fiber bundle including a plurality of optical fibers isarranged with an end portion thereof located at a position in theneighborhood of a light emitting section, the substantial portion of thelight radiated from the light emitting section enters the fiber bundleand hence is efficiently transmitted to the object to be exposed to thlight.

Moreover, the base member protecting the fiber bundle prevents dirts andfingers from being fixed to or from being brought into contact with thelight emitting section.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a side view schematically illustrating an embodiment of thepresent invention;

FIG. 2 is a perspective view depicting a fiber array plate;

FIG. 3 is a partial cross-sectional view showing the fiber array plate;

FIG. 4 is a cross-sectional view illustrating an optical fiber;

FIG. 5 is a side view depicting an alternative embodiment of the presentinvention; and

FIG. 6 is a side view showing a prior art example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-4, an embodiment of the present invention willbe described.

Incidentally, FIGS. 1-4 respectively show a side view of an embodiment,a perspective view of a fiber array plate, a partial cross-sectionalview of the fiber array plate, and a cross-sectional view of opticalfiber.

In FIG. 1, the structure includes a ceramic substrate 11 on which an LEDchip 12 is disposed by the die bonding and wire bonds 13 are disposed inthe LED chip 12 for each light emitting section 12a so as to supplyelectric power thereto. Above the light emitting section 12a of the LEDchip 12, there is provided via a flexible, transparent synthetic resin14 a fibre bundle 15 with an end portion 15a thereof located in thevicinity of the light emitting section 12a. The fiber bundle 15 isretained by use of a base member 16 so that there is formed a fiberarray plate 17 (to be described later) by use of the base member 16 andthe fiber bundle 15. Reference numeral 18 indicates spacers used tosupport the fiber array plate 17 on the ceramic substrate 11. Referencenumeral 19 is such an object to be exposed to the light as aphotosensitive drum arranged in the vicinity of another en portion 15bof the fiber bundle 15.

Next, the fiber array plate 17 will be described in detail. As shown inFIG. 2, in a base member 16 made of a glass, a synthetic resin, or thelike having a rectangular form and a thickness of about 1 mm, there isburied a fiber bundle 15 in the longitudinal direction thereof. Thefiber bundle 15 is, as shown in FIG. 3, of a construction in which aplurality of optical fibers 21 each having a diameter of 10-25 μm (to bedescribed later) are gathered. Moreover, the optical fiber 21 has a3-layer structure comprising, as shown in FIG. 4, a core 22 made of aglass having a large value of the refractive index, a clad 23manufactured with a glass having a small value of the refractive indexin the periphery of the core 22, and an absorber 24 made of carbon andthe like in the periphery of the clad 23.

A description will be given of an LED array head described above. InFIG. 1, the light radiated from the light emitting section 12a of theLED chip 12 entirely passes through the transparent synthetic resin 14and enters the fiber bundle 15 via the end portion 15a. The light istransmitted through the fiber bundle with a transmission efficiency ofat least 90% and is radiated from the another end 15b onto the object 19to be exposed to the light. Incidentally, since the distance between theend portion 15b of the fiber bundle 15 and the object 19 is quite small(about 0.2 mm in this embodiment), the substantial portion of the lightradiated from the end portion 15b of the fiber bundle is used toirradiate the object 19.

Next referring to FIG. 5, another embodiment of the present inventionwill be described. Here, the components of the embodiment of FIG. 5which are same as those of FIG. 2 will be assigned with the samereference numerals and the description thereof will be omitted.

The representative feature of this embodiment resides in a fiber arrayplate 31. The fiber array plate 31 includes a fiber bundle 15 identicalto that of the embodiment of FIG. 2 and a base member 32 which has across section having a substantially shape to bury and to retain thefiber bundle 15. Since the cross section of the base member 32 has ashape, the base member 32 can be mounted on the ceramic substrate 11without using spacers.

It is to be appreciated that the present invention is not restricted bythose embodiments, which can be modified in various fashions, forexample, to retain the fiber array plates 17 and 31 with a member otherthan the ceramic substrate 11.

According to the present invention having the configuration andoperations as described above, the following effects will be obtained.

○1 Since the resolution developed on the surface of the object to beexposed to the light is known to be independent of the thickness of thefiber plate, the thickness can be reduced to the possible extent in therange allowable with respect to the strength of the fiber plate andhence the distance between the light emitting section and the object canbe minimized, which enables to miniaturize the system.

○2 Due to the satisfactory light collecting efficiency, the energy toemit light to be supplied to the LED chip can be reduced, which enablesto minimize the capacity of the power source driving the LED array andfurther to elongate the life of the LED array.

○3 Since this configuration does not require the focusing operationwhich has been required for the rod lens array of the self-convergencetype, the assemblage of the system is facilitated.

○4 Because the base member retaining the fiber bundle protects the LEDarray, fingers and the like are prevented from being brought intocontact with the LED array, which prevents the LED array from beingdamaged.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not restricted by thoseembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can modify and change the embodimentswithout departing from the scope and spirit of the invention.

What is claimed is:
 1. An LED array head assembly comprising:alongitudinal base member; two supporting members disposed orthogonallyto said base member for supporting said base member; a ceramic substratefor supporting said supporting members; an LED chip disposed on saidsubstrate; a transparent resin disposed on said LED chip; a bundle ofoptical fibers having one end seated on said transparent resin, and theother end retained in position by said base member; said base member,supporting members and ceramic substrate forming an enclosure forcontaining said LED chip, said transparent resin and said bundle ofoptical fibers.
 2. An LED array head assembly as in claim 1 wherein saidbase member comprises a slot in which said fiber bundle is encompassed.3. An LED array head assembly as in claim 1 wherein said base member andsaid supporting members are formed as an integral unit.
 4. An LED arrayhead assembly as in claim 1, including wire bonds connected to said chipfor applying electrical power to said chip.